Spectral amplitude and phase measurements of optical signals are often desired to characterize the signals in the time domain. These spectral measurements allow time varying optical characteristics of the optical signals to be studied by means of the Fourier transform. An example of a time varying optical characteristic is a chirp of a modulated laser, i.e., variations of the laser optical frequency with intentionally induced intensity modulation. In addition, the spectral phase measurements can be used to learn about dispersive properties of an optical fiber or other optical materials or components. Various optical analyzers have been developed to measure the amplitude and phase of optical signals.
Some optical analyzers for measuring the phase of optical signals require optical filtering, which typically involves using an optical grating. A concern with these optical analyzers is that the resolution of an optical grating is inherently limited and is directly dependent on the size of the grating. In addition, optical gratings are generally expensive, which increases the cost of the optical analyzers.
Other optical analyzers for measuring the phase of optical signals require complex signal processing calculations, such as multi-dimensional autocorrelation or cross-correlation calculations of optical fields. A concern with these optical analyzers is that sophisticated processors are needed to perform the complex calculations to measure the phase.
In view of the above-described concerns, there is a need for an optical analyzer and method for measuring spectral phase of optical signals that does not require optical filtering or complex calculations, such as multi-dimensional autocorrelation or cross-correlation calculations.